The secret compartment

When rumors about the so-called ‘secret compartment’ in the BAR fuel tank first surfaced, it seemed like something out of a science fiction movie. No one other than the parties involved could be completely sure about whether this extra tank actually existed, but the court hearing confirmed its existence and made it evident that the tank itself was not actually illegal. So what was the tank for? And why was BAR slapped with a two-race ban?

The 2005 Formula 1 regulations outline 2 minimum weight requirements:
End of Saturday Qualifying: Car + Driver = 605 kgs
End of Sunday Race: Car + Driver = 600 kgs

Thanks to this year’s aggregate qualifying system, the only figure that really matters is the one measured after the first qualifying session, when there is no race fuel on board. Every team puts the bare minimum into the car – just enough for the out lap, flying lap, and in lap. So when they come into the pits, they are just above 605kgs. That’s why, the moment a car finishes a qualifying lap, the team boss or race engineer screams over the radio to ‘save fuel’.

On Sunday morning, the cars are again weighed with the driver. Of course, with race fuel now on board, the cars are a lot heavier. At the end of the race however, the drivers are weighed separately as they can’t be kept in the cars as the entire field queues up in the pit lane. Once the cars are weighed, each car’s individual weight is added to the respective driver’s weight. The total weight should be at least 600 kgs (including the mandatory minimum of 1 liter fuel onboard for FIA tests). The 5 kg relief was introduced to allow for loss of weight due to consumption of oil, brakes, tyres, other materials and even the weight of the driver. So the only variable that could account for a difference in weight from the end of first qualifying to the end of the race is fuel.

That is why the fuel drain check is conducted at random, just like a doping test. It entails draining the fuel of the car in question and then weighing it. The logic is that if the car weighs less than 600 kgs with no fuel on board, it could’ve been running as light during the race (before the pit stops).

This practice was introduced back in 1994, when refueling was made compulsory during the race. At Imola, the top three cars were drained, and all three (including Jenson Button’s BAR 007) were found to be above the limit.

In fact, Car no.3 of BAR and Jenson Button weighed 606.1kgs – safely above the limit. Apparently, cars in general finish a lot lighter than this, around the 603 kg mark. So is this what set off the alarm bells for Jo Bauer? Or was it a tip off from an ex-employee? We might never know. But he decided to dig into the matter anyway.

Using an endoscope, he examined the insides of the car’s fuel tank and found a special fuel compartment with some fuel in it. Though the compartment itself isn’t technically illegal, the fact that the fuel it carried remained inside even after draining raised questions. Then Jo Bauer emptied the said fuel and promptly got the car weighed. Voila! The car now weighed just 594.6 kgs. That was enough for the FIA to deduce that the car in question probably ran too light for a few laps during the race, giving it a speed advantage. How big could that have been? Let’s do a little math.

According to popular wisdom, a lap of the Imola circuit requires about 3 kgs of fuel. And just like the commentators keep ranting, F1 cars almost always finish the race on fumes – with a lap’s worth of fuel in the tank. That’s more than enough to accommodate the 1-liter mandatory fuel for the FIA to analyze.

Since Jenson’s BAR weighed 606.1 kgs when weighed first, we can calculate that 11.5 of fuel (606.1 kgs – 594.6 kgs) had to be drained. Nevertheless, since the car weighed 606.1kgs at the end, the car could not have run below the limit during the last stint of the race. What the FIA is looking at, however, is the couple of laps prior to each of the two stops that Jenson had taken. He had stopped at the end of lap 24 and lap 48. The final stint was for 14 laps.

However, the first stint also included the lap to the grid and the formation lap. Assuming that he was in fuel saving mode, it adds up to exactly one racing lap.

So his stop schedule, including the slowing down lap at the end, was roughly as follows:
1 lap + 24 laps + 24 laps + 14.5 laps

This means that his fuel loads were as follows:
3 kg + 72 kgs + 72 kgs + 43.5 kgs

Broken down across the 3 stints, it looks like this:
75 kgs, 72 kgs and 55 kgs (43.5 + 11.5 that got pumped out at the end)

Keeping in mind two things – that cars run on fumes on the pit-stop lap and it takes 3 kgs of fuel for each lap – the only times Jenson’s car could’ve run below the mandatory 600 kgs are laps 23/24 and 47/48.

Now the question on FIA’s mind is did the car pit when weighing just over 600 kgs or between 600 and 605 kgs, or at 596 kgs? It is estimated that a burden of 3 kgs (fuel for 1 lap at Imola) slows the car down by one tenth of a second. Depending on whether the team was using the 6-liter reserve or not, Jenson’s car would’ve been running lighter than other cars by 4 to 9 kilos. That would’ve given him anything between two tenths to three tenths per lap. Moreover, since the car would’ve run the Sunday Qualifying also lighter, it could be the secret to the higher grid position.

Strangely, nowhere in the 2005 regulations is it written that the car must weigh 600kgs ‘without fuel’. And this could exactly be the ‘hole’ that BAR’s Nick Fry and Geoff Willis cleverly exploited.

But what about the secret fuel compartment discovered by Jo Bauer? The FIA’s assertion was that it existed to hide fuel from the scrutineers so it could be used as ballast to help the car come in above the 600kg weight limit at the end of the race.

BAR’s view of it is completely different. They claimed that the tank was so big simply because that is the minimum amount of fuel the BAR007 needed for the engine to run perfectly – which is vitally important with the switch to two-race engines this year. Most teams run similar collector tanks to ensure efficient pumping of the fuel into the engine – although not all of these are as big as 9kg.

In its final judgment, the FIA said, “though the system by itself is not illegal, BAR-Honda is guilty of fraudulent conduct for trying to deceive the authorities. In designing a fuel system calculated to deceive the scrutineers into thinking the car had been drained of fuel when in fact it had not, the team was guilty of fraudulent conduct.”

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